PubMed Health⌕ Search

Biomedical subjects

R J Richards

Publications and source records attributed to R J Richards.

At least 19 recordsLinked to original sources
PubMed1992

The accumulation of pentamidine into rat lung slices and its interaction with putrescine.

The aromatic diamidine, pentamidine, accumulated into rat lung slices by an uptake system that obeyed saturation kinetics, with an average Km value of 554 microM and a Vmax value of 4077 nmol/g lung wet wt/30 min, respectively. This system was not inhibited by metabolic inhibitors but was greatly diminished by lowering the temperature from 37 degrees to 4 degrees. Both compounds, pentamidine and putrescine, inhibited the uptake of the other and the inhibition of pentamidine accumulation by putrescine was demonstrated to be non-competitive. Uptake of putrescine was inhibited by increasing concentrations of pentamidine. As putrescine accumulates in epithelial type 1 and type 2 cells and in Clara cells, it is likely that pentamidine is also accumulated in these cell types but does not utilize the pulmonary uptake system for polyamine transport. Within the time period studied, toxic effects of the drug were not observed.

Animals↗
PubMed1992

Steroid hormones during puberty: racial (black-white) differences in androstenedione and estradiol--the Bogalusa Heart Study.

A large biracial cross-section of 1038 healthy children aged 6-18 yr with 519 blacks, 519 whites, 678 males, and 360 females was evaluated for Tanner stage and serum levels of androstenedione, dehydroepiandrosterone-sulfate, estradiol, progesterone, and testosterone. The anthropometric values of the blacks and whites were very similar at each Tanner stage with only minor differences in age, height, and weight related to an earlier onset of puberty in blacks. The hormones dehydroepiandrosterone-sulfate, progesterone, and testosterone did not exhibit any racial differences. Estradiol showed a significantly higher level among black males compared to white males (P less than or equal to 0.05) whereas androstenedione was significantly higher in both white males (P = 0.0001) and females (P less than or equal to 0.01) compared with blacks. Many hormones are known to effect insulin resistance and others have reported a correlation between insulin levels and androstenedione. Blacks suffer disproportionately from diabetes. Since puberty is a time of dramatic changes in insulin resistance, racial (black-white) differences in steroid hormone changes were explored. This study shows that a racial difference in androstenedione levels exist during puberty, at a time when racial differences in insulin resistance are becoming manifest.

Adolescent↗
PubMed1991

Diamine uptake by rat lung type II cells in vitro.

Lung epithelial type II cells are responsible for synthesising and secreting pulmonary surfactant which reduces surface tension and prevents lung collapse. Type II cells replace type I cells and can proliferate in response to alveolar injury. An important aspect of this proliferation may be the ability of type II cells to accumulate amines actively, particularly the endogenous diamine putrescine. Putrescine is accumulated into isolated alveolar type II cells by an energy-dependent process. The uptake obeys saturation kinetics for which an apparent Km of 14.7 microM and Vmax of 130 pmol/micrograms DNA/hr was derived. The inhibitory effects of structurally similar amines on putrescine accumulation are described. As the herbicide paraquat has been suggested to share the same uptake system as putrescine from lung slice studies, this phenomenon was investigated in type II cell cultures. The results demonstrated that paraquat is a partially competitive inhibitor of putrescine accumulation in the cells. The Ki for the inhibition of putrescine uptake by paraquat in type II cells was calculated to be 69 microM, a value which closely matches the Km for paraquat (70 microM) predicted from lung slice studies. In molecular terms, the partial nature of the competition indicates that paraquat and putrescine do not occupy identical sites. Saturation of its site by paraquat reduced the affinity of putrescine 3.6-fold, but did not abolish it.

Animals↗
PubMed1991

Biochemical and cellular mechanisms of pulmonary fibrosis.

This review summarizes the manner in which a variety of agents may induce fibrogenic reactions in the lung. The extent of reaction is dependent on dose, time scale of exposure, and chemical reactivity. The regime of multiple dosing with chemicals or gases with recovery periods is important in disease progression. The means by which biochemists and histopathologists assess fibrosis, the advantages and disadvantages of each of the methods as related to subjectivity, quantitation, and speed of analysis are compared. The mechanisms which control the step from fibrogenesis (a potentially reversible reaction) to fibrosis (irreversible) may be linked to the maturation of collagen, calcification, or the formation of cross-linked protein masses. Attention is given to hydroxylysine cross-links in newly formed "fibrotic" collagen but focusses on gamma-glutamyl-epsilon-lysyl cross-links formed by calcium-dependent transglutaminases. It is suggested that these enzymes, released by replacement epithelial cells, could be responsible for the formation of stabilized protein masses in the lung, thus contributing to a progressive fibrosis.

Animals↗
PubMed1990

The efficacy of triclabendazole and other anthelmintics against Fasciola hepatica in controlled studies in cattle.

In eight controlled tests 274 cattle were used to assess the efficacies of triclabendazole, albendazole, clorsulon, nitroxynil, oxyclozanide and rafoxanide against Fasciola hepatica. Against one-, two- and four-week-old early immature fluke the mean efficacies of triclabendazole given orally at 12 mg/kg were 88.1, 95.3 and 90.7 per cent, respectively. Clorsulon, nitroxynil and rafoxanide administered at recommended dose rates showed negligible activity against these stages of the parasite. Against six- and eight-week-old infections the mean efficacies of triclabendazole at 12 mg/kg were 87.5 per cent and 95.7 per cent, respectively. Against F hepatica aged six weeks, albendazole and oxyclozanide showed no activity and clorsulon, nitroxynil and rafoxanide had only slight to moderate activity. The efficacies of triclabendazole, clorsulon, nitroxynil and rafoxanide against 10- or 12-week-old parasites were 100, 99.0, 99.1 and 90.1 per cent, respectively. Albendazole and oxyclozanide showed poor efficacy against 12-week-old infections.

Administration, Oral↗
PubMed1990

Interactions between paraquat, endogenous lung amines' antioxidants and isolated mouse Clara cells.

The ability of paraquat to damage mouse lung Clara cells in the presence and absence of herbicide inhibitors is investigated using a cell culture system. Clara cell damage is assessed on the loss of nitroblue tetrazolium reductase activity and the inability to attach and spread on an extracellular matrix. Endogenous amines such as putrescine and spermidine reduce paraquat-induced damage at low concentrations indicating that they compete for the same cell surface receptor as paraquat and thus potentially block the accumulation of the herbicide. The efficacy of 10 microM exogenous putrescine as a protectant is reduced the longer the time before it is added to the cultures. Clara cells contain high levels of NADPH-dependent P-450 reductase which is required to redox cycle the paraquat and generate reactive oxygen radicals. Compounds with antioxidant properties are examined for their ability to reduce the Clara cell damage. Cystamine, the disulphide form of the naturally occurring thiol, cysteamine, and taurine, a metabolite of cystamine, both of which are accumulated in the lung, do not reduce paraquat-induced Clara cell damage. Another antioxidant, alpha-tocopherol is also ineffective but reduced glutathione (GSH), present in high quantities (3.2 mM) in clara cells, could reduce damage to the cultured cells. Cysteine, a precursor of GSH, can also prevent Clara cell damage when the concentration of paraquat is low.

Animals↗
PubMed1990

Can the blood urea nitrogen/creatinine ratio distinguish upper from lower gastrointestinal bleeding?

We wanted to know if the blood urea nitrogen to creatinine (BUN/Cr) ratio could help distinguish upper from lower gastrointestinal bleeding. We analyzed retrospectively patients admitted to our hospital for gastrointestinal bleeding over the past 5 years. A total of 126 patients represented 74 upper bleeds and 52 lower bleeds. The mean BUN/Cr ratio was significantly higher in upper than lower bleeders, 34.8 and 17.8 respectively (p less than 0.001). No lower bleeder had a ratio of greater than or equal to 36, whereas 38% of upper bleeders had a ratio of greater than or equal to 36. The BUN/Cr ratio may be an easy, cheap method of distinguishing upper from lower gastrointestinal bleeding in some cases. A BUN/Cr ratio of greater than or equal to 36 suggests upper gastrointestinal bleeding, whereas a ratio of less than 36 is not helpful in locating the source of bleeding.

Adult↗
PubMed1990

Isolation of Clara cells from the mouse lung.

A method is described for isolating Clara cells from the mouse lung that does not require the technique of elutriation. Mouse lungs totally perfused of blood are instilled with crystalline trypsin (0.25%) and incubated for the optimum time of 15 min. The lung tissue is chopped, mechanically agitated, and sequentially filtered to obtain a primary digest of 3 to 5 x 10(6) cells. Clara cells, identified routinely by histochemical localization of NADPH diaphorase, using the stain nitrotetrazolium blue (NBT), accounts for between 20 to 40% of the cells in the primary digest. Layering the cells of the primary digest on a discontinuous Percoll gradient followed by centrifugation gives rise to a major band of cells, 52% that are Clara cells (0.77 +/- 0.28 x 10(6)/mouse). A second method was devised to purify the Clara cells by simply centrifuging (32g, 6 min, 10 degrees C) the primary digest and discarding the supernatant that contained only a few NBT positive cells. When this process was repeated three times, the final pellet contained 68% Clara cells realizing 0.55 +/- 0.16 x 10(6) cells/mouse. The cells have typical Clara cell morphology as confirmed by electron microscopy and have a high level of P-450 enzymes (7-ethoxycoumarin deethylase and coumarin hydroxylase). Furthermore, the primary digests and the purified isolates contain less than 1% alveolar Type II cells, although such cells, identified by the histochemical localization of alkaline phosphatase, can be obtained by a second, more extensive digestion procedure. The simple procedure described for the isolation of mouse Clara cells could be further advanced if methods could be devised to prevent the loss of NADPH diaphorase activity during enzymatic digestion and cell centrifugation.

Animals↗
PubMed1990

Type II pneumocytes in mixed cell culture of human lung: a light and electron microscopic study.

Alveolar Type II epithelial cells dedifferentiate rapidly in vitro. Studies with animal tissue suggest that cell-cell and extracellular matrix-cell interactions are important in the retention of Type II cell morphology in vitro. Thus, in this study with human tissue, alveolar Type II cells, alveolar macrophages, and spindle cells were prepared from the same sample of lung (obtained following lobectomy for cancer, n = 3), cocultured on glass cover slips or tissue culture plastic, and studied by light microscopy with scanning (SEM) and transmission (TEM) electron microscopy for 8 days. The primary cell isolates contained approximately 45% Type II cells; the remainder were macrophages or unidentifiable cells. Clusters, made up of a single layer of cuboidal Type II cells around a central core of connective tissue (largely collagen and some elastic tissue), formed above a monolayer of spindle cells. The Type II cells were morphologically similar to those seen in vivo. The cells were still cuboidal at 8 days but had lost their lamellar bodies, which were released into the medium via the apical surface. The clusters increased in size with time (area, microns 2: day 1, 29(5-143) x 10(2); day 8, 63(10-311) x 10(2); mean(range); p less than 0.02) without changing in number per culture, suggesting Type II cell proliferation. This may have been due to factors produced by the other cells and adherence to the extracellular matrix (ECM); (free collagen fibers, present in the original preparation, spindle cells, and/or Type II cells could be responsible for presence of ECM). We propose this as a useful model for the study of human Type II epithelial cells in vitro.

Cell Differentiation↗
PubMed1990

Clara cell cultures from the mouse and their reaction to bronchiolar toxins.

The major aim of this study was to determine if small numbers of freshly isolated mouse Clara cells could be used to rapidly screen the toxic effects of a number of diverse pulmonary toxins. A short-term (20 hr) culture of functionally competent (nitotetrazolium reductase positive) Clara cells was developed. In this culture the Clara cells were allowed to attach to an extracellular matrix in 96-well multiwell plates containing a culture medium of DCCM 1 and Ultroser G (0.4%). Pulmonary toxins (a total of 26 agents with concentrations ranging from 10(-7) M to 10(-3) M) were examined for their ability to reduce the attachment efficiency of functionally competent Clara cells and TD50 values (the amount of toxin required to reduce normal attachment efficiency by 50%) were calculated. With the possible exception of some halogenated hydrocarbons, the simple toxicity test in vitro correlated well with the known effects of the bronchiolar necrotic agents in vivo. For 13 compounds studied there was a direct correlation between TD50 values in vitro and LD50 values (mostly oral) in rodents in vivo, the correlation coefficient of the regression line being 0.783.

Animals↗
PubMed1989

The biochemical and pathological changes produced by the intratracheal instillation of certain components of zinc-hexachloroethane smoke.

Zinc chloride which is formed by igniting a mixture of zinc oxide and hexachloroethane in the production of white smokes has been shown to produce oedema when given to rats as a single instillation. The oedematous reaction, as assessed by histopathology and measurements of alveolar surface protein in lavage fluid, is variable, dose-dependent, and maximal at 3 days but at sub-lethal doses it regresses after 7 days. The parent compound, zinc oxide, does not produce these effects. In some animals there is evidence of a fibrogenic response at 7 days post-exposure although it is currently unknown whether or not this effect is progressive.

Animals↗
PubMed1989

Actinomycosis: a rare cause of vesicocolic fistula.

We present a case of actinomycosis presenting as a vesicocolic fistula. There are no other such reported cases. The diagnosis, pathogenesis, and treatment of abdominal actinomycosis are reviewed.

Actinomycosis↗
PubMed1988

Comparative efficacy of triclabendazole, nitroxynil and rafoxanide against immature and mature Fasciola hepatica in naturally infected cattle.

In two trials the fasciolicidal activities of triclabendazole, nitroxynil and rafoxanide were assessed in cattle naturally infected with predominantly immature stages of Fasciola hepatica. Tablets containing 900 mg triclabendazole were administered orally at a dose rate of 12 mg/kg bodyweight. Rafoxanide and nitroxynil were used at a dose rate of 10 mg/kg, rafoxanide being given orally and nitroxynil by subcutaneous injection. Based on faecal egg counts nine weeks after treatment the efficacies were calculated to be 100 per cent for triclabendazole and 95.0 per cent for nitroxynil in the first trial and 98.4 per cent for triclabendazole and 52.9 per cent for rafoxanide 15 weeks after treatment in the second trial. In the first trial five animals from each of the three groups were slaughtered and their fluke burdens counted. Compared with the untreated control group the reductions in the fluke burdens were 96.9 per cent in triclabendazole treated cattle and 76.4 per cent in the nitroxynil treated group.

Animals↗
PubMed1988

Localization of transglutaminase activity in type II epithelial cell cultures and elevation of enzyme activity in lungs of rats instilled with quartz.

Transglutaminase activity, assessed by the incorporation of [14C]-putrescine into N-acetylated dephosphorylated beta-casein, was not detectable in sonicates of alveolar macrophages and fibroblasts but was located in all preparations of rat alveolar type II cells. Enzyme activity was induced in these cells up to 7 days in vitro but not stimulated further by the direct addition of quartz to the cultures. Transglutaminase activity in whole lung sonicates increased significantly after short-term exposure to DQ-12 quartz. An increase in the numbers of type II cells and subsequent release of activated transglutaminase, concomitant with a quartz-induced elevation in lung calcium levels and potential protein substrates, is likely to lead to an increase in protein crosslinking both in the alveolar space and interstitium.

Animals↗
PubMed1987

The fate of instilled pulmonary surfactant in normal and quartz-treated rats.

Naturally prepared radiolabelled pulmonary surfactant can be rapidly cleared from the alveolar surface to the lung tissue after intratracheal instillation into experimental rats. This clearance is both time- and dose-dependent, a large dose (10 mg/animal) becoming associated with lung tissue more rapidly than a smaller more physiological dose (0.75 mg/animal). The data indicate that extracellular dipalmitoyl-phosphatidylcholine, the major component of pulmonary surfactant, is not catabolized at the alveolar surface. Alveolar free cells (mainly macrophages) appear to play a minor role in surfactant clearance. Quartz-induced phospholipidosis does not lead to an alteration in the rate of bulk surfactant clearance from the alveolar surface, although the initial distribution of the removed phospholipid complex may change in relation to the enlarged heterogenous free cell population.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1987

Isolation, biochemical characterization, and culture of lung type II cells of the rat.

A method is described for the isolation of rat lung epithelial Type II cells using trypsin digestion of tissue to release cells for subsequent separation by Percoll gradient centrifugation. Both the concentration of trypsin and the age (body weight) of the rat affect the yield from primary digestion and the final number of Type II cells obtained. A lung weighing 1 g from a 200 g rat yields approximately 30 X 10(6) washed Type II cells (approximately 25% of the total estimated lung population). These cells have a plating efficiency of 40-50% after 48 h of culture. The cells have a high alkaline to acid phosphatase ratio (usually greater than 4.0) compared with that of alveolar macrophages (0.1) and accumulate putrescine by an active transport mechanism with an apparent KM between 8 and 14 microM. Together with studies of [3H]thymidine uptake into DNA, which is maximal between 48 and 72 h of culture, these quantitative measurements form a good basis for investigating the interactions between a number of chemical agents and Type II cells in vitro.

Aging↗